Andrew Brunson, of Black Mountain, N.C., has spent 23 years living in Turkey with his wife, daughter and two sons.
While Turkey is cooperating with both Russian Federation and Iran to wind down some of the violence in Syria, Ankara has long demanded that President Bashar al-Assad must go and has backed rebels against him.
The couple ran a Christian church in the Aegean city of Izmir.
Brunson was arrested in December 2016 for alleged links to both an outlawed Kurdish insurgent group and the network of the US -based Muslim cleric who Turkey blames for a masterminding a failed military coup that year.
"I do not accept the charges mentioned in the indictment".
Brunson's trial is one of several legal cases roiling U.S.
Turkey has also been at loggerheads with Washington over US support for the Syrian Kurdish YPG militia, which Ankara considers a terrorist organisation linked to Kurdish militants waging a decades-long insurgency in Turkish soil. The cleric, Fethullah Gulen, denies the claim.
An American pastor imprisoned in Turkey since December 2016 went on trial Monday, facing up to 35 years in prison.
USA relations with Turkey have soured recently over a number of issues, including what the US sees as Erdogan's increasingly authoritarian rule.
"Turkey's Syria policy isn't to stand with or against any country".
"There is evidence that shows Brunson was arrested due to his faith", Ismail Cem Halavurt told Reuters on the eve of the trial, saying Brunson's religious role had been "classified as aiding terror organisations".
He was arrested in the aftermath of a failed military coup in 2016, for alleged links to both the outlawed Kurdistan Workers' Party, or PKK, and a network led by US -based Muslim cleric Fethullah Gulen, who is blamed by Turkey for the coup attempt. "Our prior expectation from the hearing is ending the arrest", he said.